What is the difference between API and web services?

As per my knowledge api and开发者_开发问答 web services are used to fetch data from other websites.

So what's difference between them ?

Any Help!

EDIT

Can somebody please explain it with proper example ?

What is twitter and facebook api ? Can we say it's just a function or webservices to access their data.

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A web service is just an API in HTTP clothing.

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A web service is something delivered over the Internet for direct use by another computer (rather than a human).

An API is an Application Programming Interface. A website application might expose an API thorugh a web service. However, desktop applications like Excel or Word have APIs which have nothing to do with the web (they have VBA and COM based APIs).

Simlarly, a server application (eg. Joomla) might have a PHP based API that is used from withinthe server - ie. no web service necessarily involved.

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All web services are APIs, but not all APIs are web services. One is a subset of the other.

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1. Web Service is an API wrapped in HTTP.
2. All Web Services are API but APIs are not Web Services.
3. Web Service might not perform all the operations that an API would perform.
4. A Web Service needs a network while an API doesn't need a network for its operation.

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An API doesn't need to be web based.

Web Services may also may not perform all of the operations one would expect from a full API.

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API (application programming interface) is a list of methods and classes exposed by a programmer to use by other programmers, so eg if you use Twitter or Facebook API in your programs, you can make it cooperate with Twitter and Facebook, and do many useful things. :-)

There are many ways of exposing APIs (JAR files or RMI in Java, .net Assemblies, COM objects, DLL and .H files in C/C++, JSON over HTTP, XML over HTTP, many home-made methods).

Web Services are just yet another way of exposing API, in this case the actual execution of the exposed methods is done not on your computer, but on some other computer on the Internet (on the Web - hence name "WebServices").

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A web service can be thought of as a type of API. But for the moment, you should forget that, and just concentrate on learning what an API actually is; a precise definition of methods for interacting with a piece of software. Sometimes, this involved sending data over a network, but usually we're talking about functions that may be called from a program.

For example, there's a function called FileUtils.rm in Ruby. This is the API; when you're calling the function from a Ruby script, it always looks the same. Then there's the implementation of the API; that's the code that actually removes the file - it might look completely different in every implementation of Ruby, but you (normally) don't care about that, since you're only dealing with the Ruby API.

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Webservices available over internet.you can get information without actually having the classes or know how it works using http and soap protocols.

API is a kind of library (set of classes), you can use the functions available in that to perform some action in your application.

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Check out the wikipedia entry on web API's at http://en.wikipedia.org/wiki/Api#Web_APIs.

It's well written, though pretty much agrees with what the others here say.

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APIs exposed over web are Webservices